Conjugation is the most efficient mechanism by which bacteria exchange genetic information. The mechanism is quite complex, since it requires 25 to 30 genes which are carried on an extrachromosomal plasmid in the donor strain of bacteria. The mechanism is also extremely interesting, since it involves several stages of contact between donor and recipient strains of bacteria. Phenotypes carried by conjugative plasmids are medically quite important and include resistance to multiple antibiotics, resistance to killing by serum complement, and production of toxins and colonization factors. We aim to provide some of the detailed biochemical facts which will contribute to an understanding of bacterial conjugation at the molecular level. Our studies draw upon techniques from genetics, physiology, biochemistry and structural biology. We are developing methods for the large scale purification, and subsequent detailed characterization, of some of the most important proteins involved in conjugation, while making extensive use of genetic analysis and mutant proteins. Much of our work centers on the sex factor F outer membrane lipoprotein, TraTp, which is responsible for both surface exclusion (an effect on transfer ability) and resistance to killing by serum complement. Other studies focus on conjugation proteins involved in intercellular transport of nucleic acid, assembly of the donor sex pilus, and regulation of expresssion of donor ability.